Today marks the start of Privacy Week. It’s timely, given the reaction to Facebook’s Open Graph announcement a couple weeks ago.

As we become more dependent on digital interconnectedness to stay in the know, it’s important to consider the data trail we leave behind — and not just on social networks. Earlier this year, President Obama signed signed a one-year extension of the Patriot Act, a law that was written in response to the Sept. 11 attacks, but which critics say gives the federal government unprecedented surveillance authority over private citizens.

“Having information about other individuals is a very important way of having leverage over them,” says University of Chicago law professor Geoffrey R. Stone.